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How to Treat Plants with Black Sooty Mold

By Sarah Terry ; Updated September 21, 2017

Sooty black mold is a fungus that can appear on the surface of plant leaves, stems, twigs, branches and even fruits. The fungus does not harm or feed off the plants, but instead gets its nourishment from honeydew. Honeydew is a sticky, sweet substance that certain insects secrete. When sooty mold spores are carried by the wind and land in the honeydew, the fungus feeds on the honeydew and grows, covering the plants and causing a charcoal-like sooty coating of mold. When your plants have black sooty mold, your real problem is caused by the insects, such as aphids, whiteflies, mealybugs and scale. You can apply all the fungicide you want to your infected plants, but if you don’t get rid of these insects, you can’t eradicate the sooty mold.

Identify the bugs involved in your sooty mold infestation. Aphids, mealybugs and whiteflies all cause black sooty mold. Aphids are tiny round bugs that can be black, brown, green, yellow or red. Mealybugs are also tiny, but the females are covered in a cottony wax and the males often look like gnats.

Determine whether your sooty black mold is caused by scale. Look for tiny insects that look like small, whitish, wax-covered bumps on your plant. Use a magnifying glass to help in identifying these tiny insects.

Apply an insecticide to the affected plants if you detect aphids, mealybugs, scale or whiteflies. Select an insecticide that specifies use for these exact bugs, and follow the directions closely for application. You’ll likely need to apply the insecticide more than once.

Wash the affected plants every day with a soft cloth and water, paying special attention to the underside of leaves. Whiteflies are especially resistant to insecticides, so you may also need to use an initial application of insecticide, followed by a spray application of Safer-Soap.

Recheck the infected plants 1 week after the initial application of insecticide. If you still see active, live insects, apply another dose of spray.

 

Things You Will Need

  • Magnifying glass
  • Insecticide spray
  • Soft cloth
  • Safer-Soap
  • Yellow sticky paper (optional)

Tips

  • Another method to get rid of whiteflies is to place yellow sticky paper around the base of the affected plant. Whiteflies are attracted to the color yellow, and the sticky paper can be used as traps.
  • The sooty black appearance may remain on plants even after you've eradicated the insects that were causing the mold. Usually, the mold appearance will disappear after the end of the season.

Warning

  • Don't apply a fungicide to get rid of sooty mold. Fungicide won't help to control the sooty mold; instead you must get rid of the insects that are causing it.

About the Author

 

Sarah Terry brings over 10 years of experience writing novels, business-to-business newsletters and a plethora of how-to articles. Terry has written articles and publications for a wide range of markets and subject matters, including Medicine & Health, Eli Financial, Dartnell Publications and Eli Journals.